TP 

32.5 


YF 

HI 

UC-NRLF 


GIFT  OF 


; 


THE  NATIONAL  RESEARCH  COUNCIL 
Washington,  D.  C. 


Clean  Coal 


THE  EFFECT  OF  HIGH  ASH 

upon 

Thermal  Efficiency 

Amount  of  Boiler  Plant 

Amount  of  Transportation  Equipment 


Reprinted  by 

THE  J.  G.  WHITE  ENGINEERING  CORPORATION 

New  York 


with  the  permission  of 

THE  NATIONAL  RESEARCH  COUNCIL 
Washington,  D.  C. 


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rt 


NATIONAL  RESEARCH  COUNCIL 

ENGINEERING  COMMITTBS                                          AcrmoAaTHB  VftLUAMF.Dwiui«».v»cmc«»»u«»« 

G  A  NO  DUNN .  c  KAOLXXJI                                 DEPARTMENT  op  S  c  IENCE  AHD  RE  SEARCH  n  CHAXG*  o»  WASMSCTO*  Orms 

43  EXCHANGE  PLACE                                                                         op   THB  ROOM  327  tttatmar 

COUNCIL  OF  NATIONAL  DEFENSE 


December  13, 


Thomas  H.  Watkins,  Esquire, 

Chairman,  Committee  on  Glean  Coal, 
17  Battery  Place,  Hew  Toxic. 

Dear  Sirs 

At  the  request  of  Mr.   Frank  3.  Washburn 
and  for  the  vise  of  the  National  Coal  Association  through 
you,  the  Engineering  Conmittee  of  the  national  Research 
Council  hereby  transmits  a  report  with  charts,  prepared 
without  charge  by  The  J.G.White  Engineering  Corporation, 
on  the  effect  of  dirty  or  high  ash  versus  clean  coal  upon 
thermal  efficiency,  amount  of  boiler  plant,  and  railroad 
equipment  required  for  transportation. 

Trusting  that  this  will  be  of  use  in  this 
critical  time,  I  am, 

Very  truly  yours, 


iirman,  Engineering  Committee, 
National  Research  Council. 

QD  OPS 
Enol. 

464148 


- 

•' 


THE  J.G.WHITE  ENGINEERING  CORPORATION 

ENGINEERS  AND  CONTRACTORS 


ASSOCIATE* 

«T»  WH!T«  AND  COMPANY,  INCOftPOHATEO 

new  YORK 

JLt.WHITC    MANAOEMCNT    COKrOKATION 
HEW  YORK 

.1  O.  WHITE  AND  COMVANV,  LIMITED 
hONDON 


43   EXCHANGE    PLACE 
NEW  YORK 


*L     • 
Ibth, 


CABLE  ADDKES* 
WHITCNCCO.NCWVOUK 

CODES  USED 

WESTCMN  UNION 

•ENTLEY'S  (MINING  EDITION) 

A   B.C    »7"  COmON  II 

UEBE*S  9TAKDAHB 


Mr.  Gano  Dunn,  Chairman  Engineering  Cocmittee, 
National  Research  Council, 
#43  Exchange  Place, 
Hew  York  City. 

WASTE  DOE  TO  EXCESSIVE  ASHJ}RJCT;-CCMBITSTIBLE  IK  COAL 
Dear  Sir: 

The  elimination  as  far  as  possible  of  slate  and  other  ash- forming 
Impurities  in  coal,  before  delivery  to  railroad  cars,  will  prevent  serious 
economic  waste  in  its  utilization  and  transportation. 

It  is  very  difficult  to  completely  cover  this  subject  in  a  short 
report,  because  of  the  widely  varying  uses  to  which  coal  is  put,  but  since 
the  major  portion  of  the  coal  mined  in  this  country  is  used  for  the  generation 
of  steam,  the  actual  percentage  being  about  67$  of  the  total  coal  mined,  a 
discussion  of  this  economic  waste  in  the  generation  of  steam  will  cover  the 
most  serious  losses.     The  losses  in  other  uses  of  coal  will  be  similar,  but  of 
n  different  degree. 

These  wastes  may  be  briefly  summarized  as  follows: 

1.     Reduction  in  Heating  Value  of  Coal  Due  to  Presence  of  Ash.     The 
presence  of  ash  in  coal  not  only  reduces  its  heating  value  but  as  the  percentage 
of  ash  increases,  the  percentage  of  combustible  lost  with  the  ash  also  in- 
creases, thus  greatly  reducing  the  boiler  efficiency  and  hence  lowering  the 
economic  value  of  the  coal.     See  Chart  No.  1. 


•i/< 


-2- 


2.  Increase  in  Coal  Consumption  for  a  Given  Power.  The  reduction 
in  boiler  efficiency  greatly  increases  the  amount  of  coal  that  must  be  pur- 
chased to  produce  a  given  amount  of  work.  This  is  a  direct  financial  loss, 
since  the  consumer  is  not  only  paying  for  unnecessary  ash,  but  is  losing  good 
fuel  which  is  carried  off  through  the  boiler  grates  with  the  excessive  ash. 
See  Chart  No.  2. 

3«  Influence  of  High  Ash  on  Boiler  Capacity.  The  presence  of 
excess  ash  seriously  reduces  the  boiler  capacity,  because  sufficient  coal  can- 
not be  burned  on  the  grates  to  do  the  necessary  work.  This  is  possibly  the 
effect  which  is  felt  most  seriously  by  the  consumer,  because  he  finds  it  im- 
possible to  get  sufficient  steam  from  his  boilers  to  do  the  work  demanded  of 
them  and  is  compelled  either  to  reduce  his  output,  or  purchase  additional 
boiler  capacity.  See  Chart  Ho.  3. 

4.  Increase  in  Transportation  Equipment  due  to  High  Ash.  About  85$ 
of  all  the  coal  mined  in  this  country  is  carried  by  the  railroads,  hence  un- 
necessary ash  means  an  unnecessary  task  given  to  the  railroads.  Each  per 
cent  of  avoidable  ash  adds  to  the  work  of  the  railroads  about  3*000,000  tons 
of  unnecessary  freight  per  annum.  Some  shipments  of  coal  contain  eighteen  or 
twenty  per  cent,  non-combustible.  Such  coal  requires  65$  niore  cars  and  lo- 
comotives than  a  reasonably  clean  coal  of  say  10$  ash.  See  Chart  No.  4. 

REDUCTION  IK  HEATING  VALUE  DOE  TO  THE  PRESENCE  OF  ASH. 

The  heating  value  per  pound  of  combustible  (i.e.  ash  and  moisture- 
free  coal)  of  all  coals  approximates  15,000  B.  t.  u.  There  are  some  varia- 
tions from  this  figure,  but  as  a  general  average  it  is  about  correct.  The 


" 


The  J.  G.  White  Engineering  Corporation 

New  York  City. 


deduction  in  Hear  va/ues  due  1o 
presence  of  Ash  in  coo/. 


15000 


12000 


9000 


6000 


3000 


Loss  due  fo, 
incombustible  Ash 


Loss  due  to  Carbon 
carried  orF/'n  Ash. 


Loss  in  Boiler 
]  Operation 


Heaf  avaj/ob/e 
•  fbr  usefu./  work. 


468/0/2        16 

fter  Cent  Ash 


18       21 


CHART 


c^ 


•vt- 


-3- 


variation  in  the  heating  value  of  coal  is  consequently  largely  due  to  the 
varying  percentage  of  the  ash,  —  the  effect  of  moisture  being  less  important 
except  in  a  few  cases  of  unusual  moisture  content.  If  we  could  obtain  an  ash- 
free  coal,  we  should  expect  a  heating  value  of  about  15,000  B.  t.  u.  per  pound. 
The  heating  value  by  test  of  any  commercial  coal  is  reduced  approximately  in 
proportion  to  the  increase  in  the  percentage  of  ash,  but  its  value  as  a  heat- 
ing agent  is  reduced  more  rapidly. 

The  percentage  of  ash  has  a  distinct  influence  on  the  boiler  effi- 
ciency. As  the  quantity  of  ash  increases  in  percentage,  it  becomes  more 
difficult  for  the  fireman  to  completely  burn  the  combustible.  With  a  low 
percentage  of  ash  and  good  firing  we  expect  the  ash  removed  from  the  boiler 
to  contain  approximately  25$  of  its  own  weight  of  unconsumed  combustible.  As 
the  percentage  of  ash  increases,  the  percentage  of  combustible  lost  in  the 
ash  also  increases  very  rapidly.  With  coal  containing  a  high  ash  percentage, 
it  is  rarely  possible  to  reduce  the  percentage  of  combustible  in  the  ash  to 
under  50$  of  the  weight  of  the  ash. 

This  reduction  in  heat  value  is  shown  diagrammatic  ally  for  varying 
percentages  of  ash  in  Chart  No.  1.  The  column  at  the  left  represents  the 
heating  value  of  ash- free  coal,  those  at  the  right  the  relative  values  for 
coals  containing  varying  percentages  of  ash.  The  upper  stratum  of  each 
column  represents  the  loss  due  to  the  fact  that  the  ash  is  incombustible.  The 
second  stratum  shows  an  additional  loss  due  to  the  presence  of  unconsumed  con- 
bustible  contained  in  the  ash  taken  from  boiler  grates.  The  next  stratum 
represents  the  loss  due  to  the  fact  that  steam  boilers  cannot  be  operated 
at  100$  efficiency.  The  lowest  stratum,  therefore,  represents  the  relative 


The  J.  G.  White  Engineering  Corporation 
New  York  City. 


Pounds  of  Coal  consumed  fo  produce  One  Boiler  H.P. 


234 

Pounds  of  Coal  per  BH.P. 





conmercial  values  of  coal  containing  varying  percentages  of  ash. 

DTCRSA.SE  OF  COAL  COESmiPTION  FOR  A  &IVEE  POWER. 

On  the  basis  of  Chart  No.  1,  Chart  No.  2  has  been  plotted.  This 
shows  the  pounds  of  coal  required  to  produce  one  boiler  horsepower  with 
coal  of  varying  percentages  of  ash  with  careful  operation.  It  will  be 
noted  that  for  the  best  coal  with  4$  ash,  there  is  required  approximately 
3  pounds  of  coal  per  boiler  horsepower  hour,  and  that  with  10$  ash,  less 
than  3~l/2  Ibs.  is  required.  Beyond  this  point  the  increase  is  very  rapid 
irntil  for  21$  ash  the  coal  consumption  amounts  to  5.45  pounds  per  boiler 
horsepower  hour;  80$  more  than  with  4$  s.sh  and  about  60$  more  than  with 
ash. 


INFLUENCE  OF  HIGH  ASH  ON  BOILER  CAPACITY. 

The  increase  in  the  ash  content  of  coal  seriously  reduces  the 
capacity  of  steam  boilers.  The  excessive  quantity  of  coal  required  to 
deliver  a  horsepower  with  poor  coal,  as  shown  by  chart  No.  2,  makes  it 
impossible  to  consume  sufficient  coal  on  the  grate  to  deliver  the 
necessary  boiler  horsepower.  Central  stations  today  are  in  a  very 
serious  condition  because  they  find  that  their  station  load  is  increasing, 
but  that  the  quality  of  coal  has  very  much  decreased,  necessitating  the 
operation  of  a  larger  number  of  boilers.  They  find  that  whereas  their 
boiler  houses,  two  or  three  years  ago,  were  of  sufficient  size  to  handle 
all  ordinary  increase  in  power  demands,  now,  because  of  the  poor  quality 
of  coal,  they  find  it  difficult  to  provide  the  steam  necessary  to  carry 
the  station  load.  Ufc  to  within  the  past  two  years  it  was  considered  good 


. 


• 




. 


The  J.G.  White  Emineering    Corporation. 
New  >fcrk  City. 


Number  ofSOO  HP.  Boilers  required  fo 
generate  30O,  OOO  pounds  steam 
per  Hour. 


/   2345  6  78  9  10  /I  12  13 14  /5  /6  /7 /8  /9  2O 


00 


oo 


00 


oo 

a  o 


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OQ 
aa 

aa 

00 
aa 

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tool   OQ    oo 


OO 


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too  po 

£sHis 


cj;     8 


no 

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po  po 

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00 


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88 


Number  of  Boilers. 


CHART 


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€ 


practice  to  operate  central  station  boilers  at  2CC$  to  250$  of  their 
rated  capacity  during  peak  periods.     In  the  same  stations  it  is  now 
difficult  to  operate  the  boilers  at  more  than  150$  to  160$  of  their 
rating,  and  sometimes  at  even  less.     It  is,  therefore,  necessary  for 
these  stations  to  place  more  boilers  on  the  line,  and  in  many  cases 
they  have  been  compelled  to  purchase  additional  boiler  units  at 
unusually  high  prices. 

This  phase  of  the  subject  is  illustrated  on  Chart  Ho.  3, 
which  shows  the  number  of  500  horsepower  boilers  required  to  generate 
300,000  pounds  of  steam,  equivalent  to  a  peak  load  of  15,000  to  20,000  k.w. 

With  coal  containing  £$  ash  or  less  eight  boilers  can  be  made 
to  do  this  work.     If  the  ash  runs  higher  than  6^  nine  boilers  must  be 
operated,  above  10$  eleven  boilers  would  be  required,  and  above  18$ 
nineteen  or  twenty  boilers  are  required.     This  situation  is  so  bad  that 
practically  every  large  central  station  today  has  no  spare  boiler 
capacity,  unless  spare  boilers  have  been  purchased  and  installed  within 
the  past  two  years.     They  are  compelled  to  refuse  new  business  and  must 
often  keep  boilers  in  service  that  should  be  undergoing  cleaning  and 
furnace  repairs. 

The  effect  upon  industrial  plants  is  similar  to  that  experienced 
by  the  central  stations,  but  in  a  different  degree.     Industrial  plants  do 
not  operate  their  boilers  at  the  high  ratings  experienced  in  central 
station  practice,  but  they  do  not  as  a  rule  carry  so  large  a  percentage 
of  spare  boiler  equipment  as  do  the  central  stations.     They,  therefore. 


90   080   £• 


find  it  necessary  to  operate  their  entire  boiler  equipment,  or  curtail 
production,  and  their  boilers  are  kept  in  service  for  longer  periods 
than  is  good  practice.     It  is  impossible  to  take  the  boilers  out  of 
service  long  enough  to  properly  clean  them  from  scale  and  to  properly 
repair  baffles  and  brick  work  in  the  furnaces.     The  consequence  is 
that  the  boiler  efficiency  is  seriously  reduced  until  they  are  in  such 
poor  condition  that  they  must  be  shut  down  for  cleaning,  at  the  expense 

of  production.     With  reasonably  clean  coal  this  situation  would  not 
exist. 

IHCKEA3E  IN  TBAKSPOBTATIOff  SQUIPMSHT  PEE  TO  HIGH  ASH. 

There  is  a  difference  between  preventible  and  non-preventible 
non-combustible  in  coal.     The  non-preventible  ash  is  so  thoroughly 
incorporated  with  the  structure  of  the  coal  that  it  cannot  be  separated 
mechanically.     This  minimum  ash  content  differs  in  each  mine. 

By  preventible  ash  is  meant  the  slate  and  other  impurities 
which  can  be  separated  by  careful,  preparation.     This  minimum  ash  varies 
from  as  low  as  2$  in  some  cases  to  as  high  as  33$  in  other  cases.     The 
average  for  the  country  is  probably  about  9$  or  10$.     The  percentage  of 
ash  in  the  coal  from  various  States,  together  with  the  output  for  the 
year  1915  is  given  in  Table  I.     Over  half  the  coal  mined  shows  an  ash 
analysis  of  <$  or  better.     The  percentage  for  the  country  if  averaged 
in  proportion  to  each  State* s  production  is  about  9.9$.     We  may,  there- 
fore, consider  10$  as  a  fair  average  for  clean  coal  for  the  entire 
country. 


fjCt> 


i 


. 


-7- 


TABLE  I 


TONS  OP  COAL  MIKED  IB  1915  AND  THE  PER  CENT.  OP 


ASH  IN  THE  COAL 


1  PRINCIPAL  COAL 


Coal  mined  per  annum. 
Tona  (2000 


Average  per  oent. 
of  unavoidable  ash 


Pennsylvania 
West  Virginia 
Illinois 
OMo 

Kentucky 
Indiana 
Alabama 
Colorado 
Virginia 
Iowa 
Kansas 
Wyoming 
Tennessee 
Other  States 


158,000,000 
77,000,000 

59,000,000 
22,500,000 
21400,000 
17,000,000 
15,000,000 

8,600,000 

8,100,000 

7,600,000 

6,800,000 

6,500,000 

5,700,000 
29,500,000 

AVEKAGE  FOR  THE  COUHTBY 


1255 


The  J.  G.  White  Engineering  Corporation 

New  York  City. 


Incr&as  c  d  Cars  A/b  c  Gssary  for 
Transportation  of  rf/gf)  Ash  Coa/. 

Useful  Freight  Unnecessary  freight 

4       £6      7       /       9      /O     //     /2    /J     /*     /S    /6    /7 

O     0      O     o     o    o       0     0      D     B      o     0      b  '  o      v     0 


o     o      o     o     o     o      o    • 


C 

0 


Comparative  Number  of  Cars. 


. 


ft  f*  ft't  • 


f"!  W  'ft 


PI 


PI 


PI 


There  will  be  mined  this  year  probably  six  hundred  million 
tons  of  coal.     85$  of  this  coal  will  be  transported  by  the  railroads; 
hence  for  each  per  cent,   above  the  average  10$,  the  excess  ash  will 
add  to  the  work  of  the  overburdened  railroads  5,000,000  tons  of  useless 
freight. 

Chart  No.  4  illustrates  diagranmatically  the  increased 
transportation  equipment  necessary  for  handling  coal  with  a  high  per- 
centage of  ash.     The  number  of  cars  shows  the  relative  number  of  cars 
necessary  to  carry  coals  of  varying  degree  of  ash.     The  shaded  cars 
represent  the  percentage  of  carrying  capacity  which  has  heating  value, 
the  light  cars,  the  useless  freight.     It  will  be  noted  that  in  some 
shipments  as  much  as  40$  of  the  cars  carry  worthless  material,  or  in 
other  words  coal  containing  21$  ash  requires  65$  more  cars  than  coal 
containing  10$  ash. 

In  all  these  charts  it  will  be  noted  that  the  trouble  from 
ash  is  not  excessive  until  we  pass  10$  to  12$  content.     If,  therefore, 
we  might  limit  the  percentage  of  ash  to  the  average  of  10$,  we  would 
reduce  our  transportation  equipment  to  a  practical  minimum;  we  would 
be  able  to  operate  all  boilers  at  a  reasonable  efficiency  and  would 
reduce  the  number  of  boilers  operated  to  a  little  over  one-half  of  the 
number  required  for  the  dirty  coal  (that  is  l8$  ash  or  over)  besides 
making  a  saving  in  money  that  cannot  be  accurately  estimated. 

Very  truly  yours, 
THE  J.G.  WHITE  ESGIHEEfflnU}  CORPORA! IOK. 


WAS:HD:9: 


, 


•     '  •  ''."•-'  •     • 

--.,-.  "  •:       • 

e*i£o  •  >.uc4s  .. 

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JJ1< 

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464148 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 


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